Citral enhanced sodium carboxymethyl starch-sodium caseinate compound as well as preparation method and application thereof

Abstract

The invention discloses a citral enhanced sodium carboxymethyl starch-sodium caseinate compound as well as a preparation method and application thereof. The citric aldehyde enhanced sodium carboxymethyl starch-sodium caseinate compound is prepared from the following components in parts by weight: 0.5 to 3 parts of citric aldehyde, 1.5 to 9 parts of carboxymethyl starch and 0.5 to 3 parts of sodium caseinate. According to the invention, a stable microemulsion system of sodium carboxymethyl starch / sodium caseinate is constructed for the first time, the correlation between the structural characteristics and emulsification behaviors of the sodium carboxymethyl starch, sodium caseinate and citral ternary complex is analyzed from the structural perspective, the structure and function regulation mechanism after citral microencapsulation is clarified, and stable and long-acting utilization of citral is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of deep processing of food, and specifically relates to a citral-enhanced sodium carboxymethyl starch-sodium caseinate complex and a preparation method and application thereof. Background Art

[0002] As people's requirements for the quality and safety of agricultural products increase, natural food additives or edible biological sources (plants, animals, microorganisms) that can perform additive functions have become a hot spot for scientific research and market pursuit. Citral (also known as: 3,7-dimethyl-2,6-octadiene-1-aldehyde) is a fat-soluble open-chain monoterpene compound that exists in maple oil and litsea cubeba oil. Citral has antibacterial properties and has a strong bactericidal effect on molds and bacteria. It can be added to food as a food additive to play an antibacterial and preservative role. However, citral is unstable and easily affected by external factors. It undergoes a series of chemical reactions, changes color and taste, and not only loses its original aromatic smell and function, but may even produce by-products that are harmful to the human body, posing a safety hazard. Therefore, it is very necessary to develop a method that can solve the above technical problems. Summary of the invention

[0003] The first purpose of the present invention is to provide a citral-enhanced sodium carboxymethyl starch-sodium caseinate complex; the second purpose is to provide a method for preparing the citral-enhanced sodium carboxymethyl starch-sodium caseinate complex; and the third purpose is to provide an application of the citral-enhanced sodium carboxymethyl starch-sodium caseinate complex.

[0004] The first object of the present invention is achieved in that the citrate aldehyde enhanced sodium carboxymethyl starch-sodium caseinate complex is composed of 0.5-3 parts of citrate aldehyde, 1.5-9 parts of carboxymethyl starch and 0.5-3 parts of sodium caseinate.

[0005] Preferably, the citral-enhanced sodium carboxymethyl starch-sodium caseinate complex is composed of 0.5-2 parts of citral, 3-9 parts of carboxymethyl starch and 0.5-2 parts of sodium caseinate.

[0006] Preferably, the citral-enhanced sodium carboxymethyl starch-sodium caseinate complex is composed of 1 part of citral, 3 parts of carboxymethyl starch and 1 part of sodium caseinate.

[0007] Sodium carboxymethyl starch (CMS) is an anionic starch ether that is tasteless, non-toxic, not prone to mildew, and easily soluble in water. Food-grade sodium carboxymethyl starch is widely used in products such as milk, beverages, frozen foods, fast food, cakes, syrups, etc. In addition, CMS is physiologically inert and has no calorific value, so it can also achieve ideal results when used to make low-calorific value foods. Because it has excellent thickening, gelling and emulsifying properties, it can be used as a thickener, gelling agent and emulsifier in food processing. Therefore, early researchers proposed to partially replace gum arabic with modified starch that is carboxymethylated with hydrolyzed corn starch as a microencapsulation wall material. It was found that partial replacement of gum arabic with CMS is beneficial to increasing the solid concentration, but it is not conducive to the emulsification stability of the emulsion. The compounding of sodium carboxymethyl starch with hydrophilic colloids can increase the stability of the emulsion system. For example, the compounding system of sodium carboxymethyl starch-xanthan gum can be used for the embedding of blueberry anthocyanins and pterostilbene. It cross-links with polyacrylamide to form a hydrogel with adhesion and antibacterial properties. However, the compounding effects vary greatly depending on the type of embedding material and hydrophilic colloid.

[0008] Sodium caseinate is the main protein in cow's milk, goat's milk and human milk. Because sodium caseinate contains various amino acids required by the human body, it has high nutritional value and can also be used as a nutritional enhancer. At the same time, according to the previous screening of hydrophilic colloids, sodium caseinate, as a colloid with positive charge in hydrophilic colloids, has the potential to be effectively compounded with sodium carboxymethyl starch. Previous researchers have compounded sodium caseinate with pectin, chitosan, alcohol-soluble protein and sodium alginate. At present, there is a lack of research on the characteristics of the compound system of sodium carboxymethyl starch and sodium caseinate, and the mechanism of action between them is not clear. In addition, the application of this compound system in citral microcapsule embedding has not yet been seen.

[0009] In summary, based on the rapid development of the field of natural food additives in recent years and the applicant's research on the mechanism of action of plant extracts on the quality maintenance of agricultural products and the work basis of agricultural product storage and preservation. The present invention uses sodium carboxymethyl starch-sodium caseinate compound system as a stabilizer to prepare microemulsions, and explores the molecular mechanism of interaction between sodium carboxymethyl starch and sodium caseinate through the rheological properties, texture properties, emulsification properties, micromorphological observation, physical stability, thermal stability and storage stability of the emulsion. Citral microcapsules are prepared with the above emulsification system as the wall material and citral as the core material. The structural properties of sodium carboxymethyl starch, sodium caseinate, citral and their ternary complexes are characterized by particle size, Zeta potential, rheometer (DHR2), differential scanning calorimeter (DSC), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and other technologies, revealing the correlation between their structural properties and emulsification behavior. At the same time, the regulatory mechanism of the structure and function of citral after microencapsulation is clarified, and the stable and efficient use of citral in the food field is achieved.

[0010] The second object of the present invention is achieved by: (1) Raw material pretreatment: Sodium carboxymethyl starch and sodium caseinate were dissolved in distilled water respectively, and dissolved by high-speed stirring to prepare 10% sodium carboxymethyl starch solution (solution a) and sodium caseinate solution (solution b).

[0011] (2) Raw material ratio: The mass ratio of solution a and solution b was set to 3:1, and the speed of the electric stirrer was adjusted to 1200 r / min to fully mix the two solutions to obtain a sodium carboxymethyl starch-sodium caseinate complex (emulsion a).

[0012] (3) Hydration: Hydrate emulsion a at 4°C for 24 h to allow sodium carboxymethyl starch and sodium caseinate to react fully.

[0013] (4) Homogenization: Place the emulsion a after 24 hours of hydration into a high-speed homogenizer and homogenize at a speed of 10,000 r / min for 15 min.

[0014] (5) Emulsification: Place the homogenized emulsion a in an ice water bath, and drip citral at a rate of 1 drop per second, controlling the mass ratio of the solute in the emulsion a to the dripped citral to be 4:1, to obtain a citral-sodium carboxymethyl starch-sodium caseinate complex (material a).

[0015] (6) Freeze drying: Material a is further homogenized and placed in -80°C cold hydrazine for cooling, and then freeze-dried in a vacuum freeze drying oven to obtain citral-sodium carboxymethyl starch-sodium caseinate microcapsule powder.

[0016] The third object of the present invention is achieved by using the citral-enhanced sodium carboxymethyl starch-sodium caseinate complex in the preparation of an antibacterial agent.

[0017] The present invention constructs a sodium carboxymethyl starch / sodium caseinate stable microemulsion system for the first time, analyzes the correlation between the structural properties and emulsification behavior of the ternary complex of sodium carboxymethyl starch, sodium caseinate and citral from a structural perspective, clarifies the regulatory mechanism of the structure and function of citral after microencapsulation, and realizes the stable and long-term utilization of citral. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The citral-sodium carboxymethyl starch-sodium caseinate microcapsules have a mass ratio of sodium carboxymethyl starch to sodium caseinate of 9:1, 7:1, 5:1, 3:1, 1:1, 1:3, 1:5, 1:7, and 1:9 respectively; Figure 2Citral-sodium carboxymethyl starch-sodium caseinate microcapsule powders with mass ratios of sodium carboxymethyl starch to sodium caseinate of 9:1, 7:1, 5:1, 3:1, 1:1, 1:3, 1:5, 1:7, and 1:9 respectively; Figure 3 It is a citral-sodium carboxymethyl starch-sodium caseinate microcapsule powder with a mass ratio of sodium carboxymethyl starch to sodium caseinate of 3:1; Figure 4 The viscosity-shear rate curves of 9 ratios of citral-sodium carboxymethyl starch-sodium caseinate emulsions; Figure 5 Storage modulus / loss modulus-frequency curves of 9 kinds of ratios of citral-sodium carboxymethyl starch-sodium caseinate emulsions; Figure 6 The particle size distribution diagram of 9 ratios of citral-sodium carboxymethyl starch-sodium caseinate emulsions; Figure 7 It is the Zeta potential evaluation diagram of 9 ratios of citral-sodium carboxymethyl starch-sodium caseinate emulsions; Figure 8 The graph is a storage stability test chart of 9 ratios of citral-sodium carboxymethyl starch-sodium caseinate emulsions; Fig. 9 The figure is the embedding efficiency diagram of citral-sodium carboxymethyl starch-sodium caseinate powders with 9 ratios; Fig.10 It is the SEM picture of sodium carboxymethyl starch and sodium caseinate; Fig.11 The SEM images of citral microcapsules made of sodium carboxymethyl starch and sodium caseinate in the ratio of 9:1, 7:1, and 5:1; Fig.12 The SEM images of citral microcapsules made of sodium carboxymethyl starch and sodium caseinate in the ratio of 3:1, 1:1, and 1:3; Fig.13 The SEM images of citral microcapsules made of sodium carboxymethyl starch and sodium caseinate in a ratio of 1:5, 1:7, and 1:9; Fig.14 Fourier infrared spectra of citral-sodium carboxymethyl starch-sodium caseinate powders in 9 proportions; Fig.15 The DSC spectra of citral-sodium carboxymethyl starch-sodium caseinate powders in 9 ratios. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with the embodiments and drawings, but the present invention is not limited in any way. Any changes or substitutions made based on the teachings of the present invention belong to the protection scope of the present invention.

[0020] The citrate aldehyde enhanced sodium carboxymethyl starch-sodium caseinate complex of the present invention is composed of 0.5-3 parts of citrate aldehyde, 1.5-9 parts of carboxymethyl starch and 0.5-3 parts of sodium caseinate.

[0021] The citrate aldehyde enhanced sodium carboxymethyl starch-sodium caseinate complex of the present invention is composed of 0.5-2 parts of citrate aldehyde, 3-9 parts of carboxymethyl starch and 0.5-2 parts of sodium caseinate.

[0022] The citrate aldehyde enhanced sodium carboxymethyl starch-sodium caseinate complex of the present invention is composed of 1 part of citrate aldehyde, 3 parts of carboxymethyl starch and 1 part of sodium caseinate.

[0023] The preparation method of the citral-enhanced sodium carboxymethyl starch-sodium caseinate complex of the present invention specifically comprises: (1) Raw material pretreatment: Sodium carboxymethyl starch and sodium caseinate were dissolved in distilled water respectively, and dissolved by high-speed stirring to prepare 10% sodium carboxymethyl starch solution (solution a) and sodium caseinate solution (solution b).

[0024] (2) Raw material ratio: The mass ratio of solution a and solution b was set to 3:1, and the speed of the electric stirrer was adjusted to 1200 r / min to fully mix the two solutions to obtain a sodium carboxymethyl starch-sodium caseinate complex (emulsion a).

[0025] (3) Hydration: Hydrate emulsion a at 4°C for 24 h to allow sodium carboxymethyl starch and sodium caseinate to react fully.

[0026] (4) Homogenization: Place the emulsion a after 24 hours of hydration into a high-speed homogenizer and homogenize at a speed of 10,000 r / min for 15 min.

[0027] (5) Emulsification: Place the homogenized emulsion a in an ice water bath, and drip citral at a rate of 1 drop per second, controlling the mass ratio of the solute in the emulsion a to the dripped citral to be 4:1, to obtain a citral-sodium carboxymethyl starch-sodium caseinate complex (material a).

[0028] (6) Freeze drying: Material a is further homogenized and placed in -80°C cold hydrazine for cooling, and then freeze-dried in a vacuum freeze drying oven to obtain citral-sodium carboxymethyl starch-sodium caseinate microcapsule powder.

[0029] The application described in the present invention is the application of the citral enhanced sodium carboxymethyl starch-sodium caseinate complex in the preparation of an antibacterial agent.

[0030] The present invention will be further described below with specific embodiments: Example 1 Preparation of Citral Enhanced Sodium Carboxymethyl Starch-Sodium Caseinate Complex (1) Raw material pretreatment: Sodium carboxymethyl starch and sodium caseinate were dissolved in distilled water respectively, and dissolved by high-speed stirring to prepare 10% sodium carboxymethyl starch solution (solution a) and sodium caseinate solution (solution b).

[0031] (2) Raw material ratio: The mass ratio of solution a and solution b was set to 3:1, and the speed of the electric stirrer was adjusted to 1200 r / min to fully mix the two solutions to obtain a sodium carboxymethyl starch-sodium caseinate complex (emulsion a).

[0032] (3) Hydration: Hydrate emulsion a at 4°C for 24 h to allow sodium carboxymethyl starch and sodium caseinate to react fully.

[0033] (4) Homogenization: Place the emulsion a after 24 hours of hydration into a high-speed homogenizer and homogenize at a speed of 10,000 r / min for 15 min.

[0034] (5) Emulsification: Place the homogenized emulsion a in an ice water bath, and drip citral at a rate of 1 drop per second, controlling the mass ratio of the solute in the emulsion a to the dripped citral to be 4:1, to obtain a citral-sodium carboxymethyl starch-sodium caseinate complex (material a).

[0035] (6) Freeze drying: Material a is further homogenized and placed in -80°C cold hydrazine for cooling, and then freeze-dried in a vacuum freeze drying oven to obtain citral-sodium carboxymethyl starch-sodium caseinate microcapsule powder.

[0036] Example 2 Referring to the preparation method of Example 1, the mass ratio of sodium carboxymethyl starch and sodium caseinate in the raw material ratio (2) was set to 9:1, 7:1, 5:1, 3:1, 1:1, 1:3, 1:5, 1:7, and 1:9, and the mass ratio of citral added dropwise in the emulsification (5) was set to 4:1. After hydration, homogenization, and emulsification, 9 citral-sodium carboxymethyl starch-sodium caseinate emulsions with different ratios were obtained.

[0037] The viscosity and modulus of the above emulsions were measured using a rheometer (DHR2). Viscosity: Select the flow-ramp test mode, use a 60mm flat plate as the fixture, fix the measurement gap to 500μm, the shear rate range is 0.1~100 s-1, the temperature is 25℃, the equilibrium time is 60s, the duration is 120s, and the data acquisition uses the logarithmic mode. Linear viscoelastic region: Select the Oscillation Amplitude test mode, select the test temperature as 25℃, set the angular frequency to 10.0rad / s, the strain range is 0.001%~100%, and take a point for every 10 units of strain change. Frequency sweep: Select the Oscillation frequency sweep test mode, the test temperature is 25℃, the frequency range is 1.0~100rad / s, the data acquisition mode is the logarithmic mode (log), take 10 points for each order of magnitude, and perform an oscillation sweep test.

[0038] The results are as follows: (1) Viscosity-shear rate curve like Figure 4 As shown in the figure, with the increase of shear rate, the viscosity of the five ratios of sodium carboxymethyl starch-sodium caseinate-citral emulsions, namely 9:1, 7:1, 5:1, 3:1, and 1:1, gradually decreases, showing a typical shear thinning phenomenon. The rate of viscosity reduction decreases from fast to slow, and eventually tends to zero. This may be because when the shear force reaches a certain critical value, the spatial structure of the emulsion is squeezed and deformed, resulting in the breaking of hydrogen bonds. At the same time, at the same shear rate, with the increase of the content of sodium carboxymethyl starch, the viscosity of the composite emulsion gradually increases, which may be related to the presence of a large amount of negative charges on the surface of sodium carboxymethyl starch.

[0039] (2) Storage modulus G' / loss modulus G"-frequency curve Frequency sweeps are often used to evaluate the viscoelasticity of a sample and the stability of its internal structure. Figure 5 As shown in the figure, the five ratios of 9:1, 7:1, 5:1, 3:1, and 1:1 all show the situation of G'>G", indicating that the five sample systems are mainly elastic components, while the four ratios of 1:9, 1:7, 1:5, and 1:3 belong to viscous fluids. It can be seen from the figure that the storage modulus and loss modulus of the five ratios of 9:1, 7:1, 5:1, 3:1, and 1:1 increase with the increase of frequency, and G' is always higher than G", showing gel-like characteristics. At the same time, with the increase of the proportion of sodium carboxymethyl starch, the values ​​of the storage modulus and loss modulus of the emulsion system also show a significant upward trend. It is inferred that sodium carboxymethyl starch and sodium caseinate can interact with each other and produce different degrees of cross-linking at different mass ratios, thereby reducing the destruction process of the emulsion system at the oscillation frequency, and finally showing good stability.

[0040] Example 3 Referring to the preparation method of Example 1, the mass ratio of sodium carboxymethyl starch and sodium caseinate in the raw material ratio (2) was set to 9:1, 7:1, 5:1, 3:1, 1:1, 1:3, 1:5, 1:7, and 1:9, and the mass ratio of citral added dropwise in the emulsification (5) was set to 6:1. After hydration, homogenization, and emulsification, 9 citral-sodium carboxymethyl starch-sodium caseinate emulsions with different ratios were obtained.

[0041] The particle size of the above emulsion was measured by a laser particle size analyzer. The stirring speed was set to 2500r / min, and the sample was dispersed in distilled water to an appropriate shading value (1~10%) to avoid multiple light scattering effects. Three parallel measurements were performed, and the volume-weighted average value D(4,3) was used to represent the average particle size of the emulsion droplets and a particle size distribution diagram was drawn.

[0042] Generally speaking, the particle size of microcapsules is 5-200μm. If the particle size of microcapsules is too small, its embedding rate will be limited, but if the particle size is too large, it will easily break, thus affecting the sustained release effect. Figure 6 As shown in the figure, the particle size of the microcapsule emulsion is mainly between 10-100 μm, and the particle size distribution of the ions contained in the emulsion is relatively uniform. A small peak appears in the range of 5-10 μm, which may be due to the excessive content of sodium caseinate in the emulsion, which fails to completely form a complex with sodium carboxymethyl starch and citral. Overall, the average particle size under the optimal preparation process conditions is 39.81 μm, and the particle size is normally distributed, indicating that the particle size of sodium carboxymethyl starch-sodium caseinate-citral microcapsules is relatively uniform.

[0043] Example 4 Referring to the preparation method of Example 1, the mass ratio of sodium carboxymethyl starch and sodium caseinate in the raw material ratio (2) was set to 9:1, 7:1, 5:1, 3:1, 1:1, 1:3, 1:5, 1:7, and 1:9, and the mass ratio of citral added dropwise in the emulsification (5) was set to 8:1. After hydration, homogenization, and emulsification, 9 citral-sodium carboxymethyl starch-sodium caseinate emulsions with different ratios were obtained.

[0044] The potential of the emulsion was measured using a nanoparticle size potential analyzer.

[0045] The stability of microcapsules in suspensions can be evaluated using Zeta potential. The amount of charge on the surface of the emulsion can be measured, and the long-term stability of the emulsion can be inferred based on this. Generally, when the absolute value of the Zeta potential is above 30mV, it is believed that there is a strong enough electrostatic repulsion between the droplets of the sample to overcome the aggregation of the emulsion, thus having good long-term storage stability. The larger the absolute value, the higher the stability of the system. When the potential value is too low, the emulsion is prone to sedimentation due to aggregation, and even the balance of the emulsion system is destroyed, resulting in phase separation. Figure 7 As shown in the figure, in the sodium carboxymethyl starch-sodium caseinate-citral microcapsules, with the increase of sodium caseinate content, the Zeta potential dropped from -30.73mV to -39.2mV and then rose to -23.5mV. When the mass ratio of sodium carboxymethyl starch to sodium caseinate was 3:1, the Zeta potential was -39.2mV, which shows that the microcapsules at this mass ratio are stable.

[0046] Example 5 Referring to the preparation method of Example 1, the mass ratio of sodium carboxymethyl starch and sodium caseinate in the raw material ratio (2) was set to 9:1, 7:1, 5:1, 3:1, 1:1, 1:3, 1:5, 1:7, and 1:9, and the mass ratio of citral added dropwise in the emulsification (5) was set to 10:1. After hydration, homogenization, and emulsification, 9 emulsions of citral-sodium carboxymethyl starch-sodium caseinate in different ratios were obtained.

[0047] The storage stability test of the above emulsion was carried out. 15 mL of the emulsion was placed in a glass tube and placed at 4°C for 1, 7 and 21 days, and the state changes were observed.

[0048] like Figure 8 As shown in the figure, the mass ratios of sodium carboxymethyl starch and sodium caseinate from left to right are 9:1, 7:1, 5:1, 3:1, 1:1, 1:3, 1:5, 1:7, and 1:9, respectively, and from top to bottom are the states of the emulsion at 4°C for 1, 7, and 21 days. During the 21-day storage process, the emulsion maintained a good emulsified state, and no obvious stratification occurred due to the decrease in temperature and the extension of time. This is because sodium carboxymethyl starch, as a thickener and stabilizer, forms a protective film around the emulsion, and sodium caseinate, as an emulsifier, reduces the surface tension, allowing the oil phase and the water phase to mix better. The combined effect of the two maintains the stability of the emulsion. After long-term storage, the color of the emulsion deepened slightly, which may be due to the slow oxidation reaction of the active functional groups contained in citral during storage. In general, the emulsion has good stability and is suitable for long-term storage.

[0049] Example 6 Referring to the preparation method of Example 1, the mass ratio of sodium carboxymethyl starch and sodium caseinate in the raw material ratio (2) was set to 9:1, 7:1, 5:1, 3:1, 1:1, 1:3, 1:5, 1:7, and 1:9, and the mass ratio of citral added dropwise in the emulsification (5) was set to 4:1. After hydration, homogenization, emulsification, and freeze-drying, 9 citral-sodium carboxymethyl starch-sodium caseinate powders with different ratios were obtained.

[0050] The embedding efficiency of the above powder was measured. Weigh 1.5 g of the prepared microcapsule powder accurately, shake it with 30 mL of petroleum ether for 3 minutes, filter it, and then wash the solid residue on the filter paper with 10 mL of petroleum ether. Repeat this operation 3 times and combine the filtrate. Transfer the washing liquid to a beaker with constant weight in advance and place it in a 70°C water bath to evaporate the petroleum ether. When there is no obvious petroleum ether liquid, dry the beaker in a 70°C oven for 1 hour and weigh it every 0.5 hours until the mass of the dry flask before and after weighing does not exceed 0.1 mg. Weigh it accurately and calculate the surface oil content according to formula (1).

[0051] Surface oil content (m1) = (M1-m0) / M (1) M1-weight of the beaker after drying, g; m0-mass of the empty beaker, g; M-mass of the sample, g.

[0052] Accurately weigh 1.5 g of microcapsule powder, add 10 mL of 60 °C distilled water to fully dissolve, pour into a separatory funnel and add 1 mL of ammonia water to shake well, add 10 mL of anhydrous ethanol, shake well, then add 25 mL of ether, shake well to release gas and add 25 mL of petroleum ether, let stand to separate, take the upper layer, evaporate the petroleum ether and ether in a 70 °C water bath, then place in a 70 °C oven to dry, accurately weigh, and calculate the total essential oil content according to formula (2).

[0053] Total oil content (m2) = (M1-m0) / M (2) M2-weight of the beaker after drying, g; m0-mass of the empty beaker, g; M-mass of the sample, g.

[0054] Calculation of embedding rate: R=1-m1 / m2 (3) m1-surface oil content, g; m2-total oil content, g The compounding of sodium carboxymethyl starch and hydrophilic colloid can increase the stability of the emulsion system, while sodium caseinate, as a colloid with positive charge in the hydrophilic colloid, can increase the stability of the emulsion system when compounded with sodium carboxymethyl starch, but different mass ratios of the two will produce different effects. Fig. 9As shown, the mass ratio of sodium carboxymethyl starch and sodium caseinate is set to 9:1, 7:1, 5:1, 3:1, 1:1, 1:3, 1:5, 1:7, 1:9, and the embedding rates are 56.25%, 64.71%, 77.36%, 83.87%, 74.55%, 70.83%, 60.61%, 53.85%, 52.17%, respectively. When the mass ratio of sodium carboxymethyl starch and sodium caseinate is 3:1, the embedding rate reaches a maximum value of 83.87%, and then with the increase of sodium caseinate content, the embedding rate begins to decrease, which may be because the viscosity of the emulsion increases with the excessive content of the emulsifier, the molecular mobility is blocked, and citral cannot enter the interior of sodium carboxymethyl starch-sodium caseinate.

[0055] Example 7 Referring to the preparation method of Example 1, the mass ratio of sodium carboxymethyl starch and sodium caseinate in the raw material ratio (2) was set to 9:1, 7:1, 5:1, 3:1, 1:1, 1:3, 1:5, 1:7, and 1:9, and the mass ratio of citral added dropwise in the emulsification (5) was set to 6:1. After hydration, homogenization, emulsification, and freeze-drying, 9 citral-sodium carboxymethyl starch-sodium caseinate powders with different ratios were obtained.

[0056] The powder was observed for microscopic morphology using a scanning electron microscope. About 10 mg of citral microcapsules were dispersed on a sample table with a conductive adhesive, and the excess powder was blown off. After gold spraying, the structure was observed using a scanning electron microscope. The electron gun acceleration voltage was 15 Kv.

[0057] Figure 11-13 The SEM images of citral microcapsules made from different proportions of sodium carboxymethyl starch and sodium caseinate show that their morphology is irregular blocks of different sizes, while the morphology of sodium carboxymethyl starch and sodium caseinate powder is uniformly spherical, indicating that the morphology of citral and sodium carboxymethyl starch-sodium caseinate has changed greatly during the preparation of microcapsules. It is preliminarily judged that the molecules of the three interact with each other during the vacuum freeze-drying process, changing the original morphology of sodium carboxymethyl starch and sodium caseinate, generating a new phase, and finally forming microcapsules. In addition, when magnified at the same multiple, the surfaces of microcapsules made from different mass ratios have multiple pores with different pore sizes and overall diameters, and as the content of sodium caseinate continues to increase, the holes on the surface gradually become smaller and fewer, but there is always a certain number. When the mass ratio is 9:1, 7:1, the surface is rough, the structure is complex, and the hole size is uneven, which may be due to the excessive content of sodium carboxymethyl starch and insufficient emulsifier. However, when the mass ratio is 3:1, the pores are evenly distributed, the overall diameter is reduced, and the pore size distribution is orderly, which corresponds exactly to the DSC analysis results.

[0058] Example 8 Referring to the preparation method of Example 1, the mass ratio of sodium carboxymethyl starch and sodium caseinate in the raw material ratio (2) was set to 9:1, 7:1, 5:1, 3:1, 1:1, 1:3, 1:5, 1:7, and 1:9, and the mass ratio of citral added dropwise in the emulsification (5) was set to 8:1. After hydration, homogenization, emulsification, and freeze-drying, 9 citral-sodium carboxymethyl starch-sodium caseinate powders with different ratios were obtained.

[0059] The powder was characterized by FTIR using a Fourier transform infrared spectrometer. An appropriate amount of microcapsule powder and 150 mg of potassium bromide (dried in an oven in advance) were fully ground and made into complete, uniform, translucent flake samples by a tablet press and then measured by an infrared spectrometer. The spectral scanning range was 400~4000cm −1 .

[0060] Fourier transform infrared spectroscopy can characterize the changes in functional groups and intermolecular interactions of biopolymers, such as Fig.14 As shown in the figure, the characteristic absorption peaks of sodium carboxymethyl starch include the stretching vibration absorption peak of hydroxyl group (3400cm -1 ), the CH stretching vibration absorption peaks of methyl and methylene (2920 cm -1 and 2850cm -1 ), the stretching vibration absorption peak of C=O in the carboxyl group (1610-1630cm -1 The characteristic absorption peaks of sodium caseinate are the stretching vibration absorption peaks of NH and OH (3400cm -1 ), the CH stretching vibration absorption peaks of methyl and methylene (2920 cm -1 and 2850cm -1 ), the absorption peak of the amide I band caused by the stretching vibration of C=O in the peptide bond (1630-1650cm -1 The absorption peak wavelengths of the two are basically the same; the characteristic absorption peaks of citral are the stretching vibration absorption peaks of C=C (1640-1680cm -1 ), stretching vibration absorption peak of aldehyde proton (2720-2740cm -1 and 2820cm -1 ). The infrared spectra of sodium carboxymethyl starch-sodium caseinate-citral microcapsules prepared with different mass ratios show that at 1600 cm -1 The C=O stretching vibration absorption peak appeared at 3400cm -1 The stretching vibration peaks of OH and NH are shown at 1630 cm, which are one of the important characteristic peaks representing sodium carboxymethyl starch and sodium caseinate. -1 The stretching vibration peak characteristic of C=C in citral appeared nearby at 2717 cm -1 and 2815cm -1The stretching vibration absorption peak of the aldehyde proton appears near the 1630cm-1 peak, which can be used to identify the aldehyde group. The results show that the infrared spectrum has almost no change, but at 1630cm-1, which represents the characteristic peak of citral, -1 At the point, with the increase of sodium caseinate content, the peak intensity shows a trend of first weakening and then strengthening, and drops to the lowest value when the mass ratio is 3:1, which may be due to the embedding of citral. When the mass ratio of sodium carboxymethyl starch to sodium caseinate is 1:1, the embedding rate is the largest, so the peak intensity of citral here is the lowest, which is consistent with the subsequent trend that with the increase of sodium caseinate content, the peak intensity increases and the embedding rate decreases.

[0061] Example 9 Referring to the preparation method of Example 1, the mass ratio of sodium carboxymethyl starch and sodium caseinate in the raw material ratio (2) was set to 9:1, 7:1, 5:1, 3:1, 1:1, 1:3, 1:5, 1:7, and 1:9, and the mass ratio of citral added dropwise in the emulsification (5) was set to 10:1. After hydration, homogenization, emulsification, and freeze-drying, 9 ratios of citral-sodium carboxymethyl starch-sodium caseinate powders were obtained.

[0062] The thermal stability of the above powder was measured using a differential scanning calorimeter. 3-10 mg of the sample was weighed and placed in a crucible, and the measurement was started on a synchronous thermal analyzer. The test temperature range was 30-600°C, the heating rate was 10°C / min, and the carrier gas was nitrogen.

[0063] like Fig.15 As shown in the figure, the samples with five ratios of 9:1, 7:1, 5:1, 3:1, and 1:1 had only one absorption peak during the heating process, and the peak temperatures were 274.90℃, 288.94℃, 279.10℃, 275.74℃, and 276.27℃, respectively. This endothermic reaction may be the melting temperature of the microcapsules. The samples with six ratios of 1:9, 1:7, 1:5, 1:3, 1:1, and 3:1 had only one exothermic peak during the heating process, and the peak temperatures were 165.20℃, 169.65℃, 173.75℃, 150.70℃, 167.61℃, and 178.61℃, respectively. This exothermic reaction may be due to the overflow of citral during the temperature increase, and an oxidation reaction occurred. The results show that sodium carboxymethyl starch-sodium caseinate-citral microcapsules are relatively stable in an environment below 150℃. Among them, the peak temperature of the exothermic peak of the sample with a ratio of 3:1 is the highest, indicating that the sample with this ratio is the most stable.

Claims

1. A citrate aldehyde enhanced sodium carboxymethyl starch-sodium caseinate complex, characterized in that The citrate aldehyde enhanced sodium carboxymethyl starch-sodium caseinate complex is composed of 0.5-3 parts of citrate aldehyde, 1.5-9 parts of carboxymethyl starch and 0.5-3 parts of sodium caseinate.

2. The citrate aldehyde enhanced sodium carboxymethyl starch-sodium caseinate complex according to claim 1, characterized in that The citrate aldehyde enhanced sodium carboxymethyl starch-sodium caseinate complex is composed of 0.5-2 parts of citrate aldehyde, 3-9 parts of carboxymethyl starch and 0.5-2 parts of sodium caseinate.

3. The citrate aldehyde enhanced sodium carboxymethyl starch-sodium caseinate complex according to claim 1, characterized in that The citrate aldehyde enhanced sodium carboxymethyl starch-sodium caseinate complex is composed of 1 part of citrate aldehyde, 3 parts of carboxymethyl starch and 1 part of sodium caseinate.

4. A method for preparing the citrate aldehyde enhanced sodium carboxymethyl starch-sodium caseinate complex according to any one of claims 1 to 3, characterized in that include: (1) Raw material pretreatment: Sodium carboxymethyl starch and sodium caseinate were dissolved in distilled water respectively, and dissolved by high-speed stirring to prepare 10% sodium carboxymethyl starch solution (solution a) and sodium caseinate solution (solution b); (2) Raw material ratio: The mass ratio of solution a and solution b was set to 3:1, and the speed of the electric stirrer was adjusted to 1200 r / min to fully mix the two solutions to obtain a sodium carboxymethyl starch-sodium caseinate complex (emulsion a); (3) Hydration: emulsion a was placed at 4°C for 24 h to allow sodium carboxymethyl starch and sodium caseinate to fully react; (4) Homogenization: Place the emulsion a after 24 hours of hydration into a high-speed homogenizer and homogenize at a speed of 10,000 r / min for 15 min; (5) Emulsification: Place the homogenized emulsion a in an ice water bath, and drip citral at a rate of 1 drop per second, controlling the mass ratio of the solute in the emulsion a to the dripped citral to be 4:1, to obtain a citral-sodium carboxymethyl starch-sodium caseinate complex (material a); (6) Freeze drying: Material a is further homogenized and placed in -80°C cold hydrazine for cooling, and then freeze-dried in a vacuum freeze drying oven to obtain citral-sodium carboxymethyl starch-sodium caseinate microcapsule powder.

5. An application of the citral-enhanced sodium carboxymethyl starch-sodium caseinate complex according to any one of claims 1 to 3, characterized in that The application of the citral-enhanced sodium carboxymethyl starch-sodium caseinate complex in the preparation of an antibacterial agent.

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